As digital media technology continues to advance and the cost of storage continues to decline, users increasingly host and consume digital media content on their own primary computers (e.g., desktop PCs). Examples of such digital media include music, video, still images, and so on. So, this means that increasingly users are listening to digital music, watching digital video, and viewing still images (e.g., photographs) on their home or business computers.
At the same time, the corresponding increase in the availability of portable media-playback devices such as personal digital assistants (PDAs), digital media players (e.g., so-called “MP3 players”), hand-held computers, laptop computers, and smart phones is providing users more ubiquitous access to digital media content than ever. As users rely more and more on such portable computing devices, there is a growing need for applications that effectively transfer digital media from source devices, such as primary computers, to the portable devices.
However, the existence of the multitude of media content formats complicates the transference of digital media content from source devices to target media-playback devices. This multitude of media content formats raises issues about format compatibility with target media-playback devices and management of legal rights for transferred media content.
Digital media content typically exists in a specified “format.” Herein, a “format” of digital media content includes its specific pre-established arrangement or organization of media data in computer-readable storage media. In addition, media data is typically compressed (and later decompressed) using a specific compression/decompression (“codec”) algorithm. Because a media format and its specified codec are often closely associated, the line between them is often blurred. Herein, unless the context indicates otherwise, references to the “format” of digital media content includes the codec associated with compressing/decompressing the content as well as the content's specific pre-established arrangement or organization of media data in computer-readable storage media.
Transcoding Media Content
Typically, a media-playback device is designed to handle one or more specific formats of the digital media content (“formatted-media-content”). Due to space, processing-power, memory, and licensing constraints, these playback devices typically have a limited set of compatible formats. Often a device manufacturer licenses the technology for playing formatted-media-content in a proprietary format, such as those formats listed above. Sometimes, the device manufacturer implements its own proprietary format technology.
Since a target playback device typically employs a different or slightly altered format than does the source device (e.g., desktop PC), the format of formatted-media-content is typically altered before being transferred from the source device to the target device. This format-alteration is commonly called “transcoding.”
A transcoding process may include, for example, converting a formatted-media-content from one format to another (e.g., MP3 to WMA) so the newly formatted content will play on the playback device. Furthermore, a transcoding process may include, for example, down-sampling the formatted-media-content to a lower bit rate to reduce the amount of storage space needed on the playback device, or adapting the screen size of the formatted-media-content so video appears correctly on the playback device.
When transcoding, the formatted-media-content is sometimes converted into a format having lower processing requirements for decoding. A formatted-media-content configured for playback on a full-scale “desktop” computer may be too complex to decode effectively on a device with a lower-powered processor, such as a portable media-playback device. Furthermore, when transcoding, the formatted-media-content is sometimes converted into a specific format (e.g., a proprietary format) employed by the target media-playback device.
Digital Rights Management
Another consideration complicating the transference of digital media content is a desire to maintain protection of the intellectual property rights in the media content owned by the vender, publisher, owner, and/or author of the content. “Digital rights management” or “digital restrictions management” (DRM) seeks to manage ownership and distribution rights for media content from its creation to its consumption.
While some of the existing digital media content format do not support DRM protection, many of the existing format do support DRM protection to some degree. Typically, a DRM-protected format is associated with one or more particular DRM products and/or standards. MPEG-4 has been actively developing a DRM standard, the Intellectual Property Management and Protection (IPMP) protocol. Several commercial DRM products are also currently available, such as MICROSOFT® WINDOWS MEDIA® RIGHTS MANAGER (WMRM) (Microsoft Corporation, Redmond, Wash.).
A DRM system such as WMRM encrypts and packages digital media content into a digital media file for super-distribution. A decryption key is uploaded to a license server along with a specification of license rights selected by the vender. To play protected content, a user first acquires a license (e.g., from the proper license server) that contains the decryption key and user access rights. A license includes the decryption key that decrypts the encrypted digital content and a description of the license rights (e.g., play, copy, etc.) conferred by the license and related conditions (e.g., begin date, expiration date, number of plays, etc.). A license to use the content is individualized and typically encrypted in such a way that the key binds to the user's hardware, making it difficult for the license to be used by others illegally.
With a DRM-protected media content, a licensed user is allowed to perform DRM-managed actions on the protected media content. In addition, a DRM system may limit the type and the extent (e.g., how many times or how often) that the user performs DRM-managed actions on the protected media content. Examples of DRM-managed actions include:                play the content;        copy the content;        transcode or convert the content;        transfer the content to a portable playback device;        “burn” the content to a compact-disc (CD) or other computer-readable media.        
With conventional multimedia products, the DRM information of DRM-protected media content is lost once the content is transcoded (or generally, transformed).